Sewing machines of this type are also referred to as needle feed sewing machines. In addition to being provided with needle feed, they can also be provided with a so-called upper feeding device for the workpiece or workpieces to be sewn.
A sewing machine is known from U.S. Pat. No. 2,292,257, wherein the upper area of a jogging frame is mounted by means of a link which is displaceable with a reciprocating motion by means of a crank mechanism approximately in the workpiece feed direction. This makes it possible for the needle to run essentially perpendicular to the workpiece when stitching into the material to be sewn. A disadvantage in this case is that a special drive is required for the mentioned crank mechanism, and that a straight-line motion of the needle can only be achieved in theory with a specific stitch length because the geometry of the crank mechanism for displacing the jogging frame in the jogging plane is invariable. Therefore, a distinct straight-line motion, i.e. displacement of the needle parallel to itself, is not achieved in the case of different stitch lengths. Furthermore, it is impossible to use such a mechanism in sewing machines in which the sewing direction for producing lock stitches can be reversed.
Because of the previously described disadvantages sewing machines having a jogging frame which can be driven with a swinging motion about a link joint have therefore gained a much greater acceptance in practice. With such a sewing machine of the defined type, which is known from U.S. Pat. No. 4,616,586, the swing drive of the jogging frame is effected by way of a needle bar feed shaft which can be driven with a swinging motion and is connected to the jogging frame via a chain of articulated levers. In addition, the jogging frame also bears a presser foot of an upper feeding device, which foot can be driven with a swinging motion together with the needle bar. As a result of the needle bar and needle being pivoted about the swivel axis of the fixed link, the needle undergoes, when stitching into the workpiece to be sewn, a bending load resulting in an increase in needle wear. A further disadvantage is that, as a result of its change in inclination during needle feed, i.e. during feed of the workpiece with the needle having stitched therein, the needle displaces the workpieces, to be sewn together, relative to one another, which can result in the two workpieces, to be sewn together, no longer being flush with one another at the end of a seam.
A zigzag-stitch machine is known from U.S. Pat. No. 3,313,258, wherein a needle bar jogging frame can be moved with a translational reciprocating motion at right angles to the sewing direction, i.e. at right angles to the workpiece feed direction, to produce the zigzag stitch. For this purpose the jogging frame is mounted on a sliding bar. Guidance of a needle bar jogging frame in such a manner in a needle feed direction, i.e. in the workpiece feed direction, is impossible.